Hazards with cracked eggs and their relationship to egg shell strength

BACKGROUND: This study examined the relationship between egg shell strength and the prevalence of cracked shells, plus the relationship between egg shell cracks and the presence of bacteria in the albumen of retail eggs. A total of 500 eggs was sampled from five supermarket stores. Each egg was assessed for shell cracks using a candling method. The strength of the shells was assessed using a penetrometer. Bacteria from the egg albumen were recovered on blood agar. RESULTS: The proportion of eggs that were cracked was on average 9%, and at one of the stores it was 17%. Albumen from eggs with gross cracks produced more abundant bacterial growth on blood agar compared to non-cracked eggs, and contained a higher incidence of Gram negative bacteria. Campylobacter spp. were not recovered from any eggs. The shells in cracked eggs had lower Shore D durometer values indicating that they were physically weaker than non-cracked eggs. CONCLUSIONS: Weaker shells were more prone to developing cracks, and cracked eggs were more likely to contain bacteria. There were substantial differences between supermarkets in the prevalence of eggs with cracked shells. (c) 2008 Society of Chemical Industry